1. Field of the Invention
The present invention relates to a light-emitting diode (LED) package structure. More particularly, the present invention relates to a surface mount device (SMD) type LED package structure.
2. Description of Related Art
Due to the advantages of long lifetime, small size, vibration resistance, low heat emission, and low power consumption, LEDs have been widely applied in various home appliances and instruments as indicators or light sources. In recent years, the LEDs are developed to be multi-colored and high luminance, so the application scope of the LEDs has been extended to mega-size outdoor display boards and traffic lights and the like, and the LEDs can even replace tungsten lights and mercury lights to serve as illuminating light sources that are both power saving and environment friendly.
FIGS. 1A and 1B are a schematic front view and a schematic side view of a conventional SMD type LED package structure respectively, and FIG. 1C is a schematic sectional view taken along a section line I-I′ of FIG. 1A. Referring to FIGS. 1A-1C, an LED package structure 100 includes an encapsulant 110, a carrier 120, an LED chip 130, and a transparent colloid 140. The encapsulant 110 includes a cavity 112 located in a front end of the encapsulant 110, and the carrier 120 includes a die pad 122 and two leads 124. The die pad 122 is disposed on the encapsulant 110 and located in the cavity 112, and the leads 124 pass through the encapsulant 110 and extend outside the cavity 112. Moreover, the LED chip 130 is disposed on the die pad 122, and is electrically connected to the leads 124. In addition, the transparent colloid 140 is filled in the cavity 112, so as to encapsulate the LED chip 130, the die pad 122, and a portion of the leads 124 exposed by the cavity 112.
Furthermore, the leads 124 of the LED package structure 100 are suitable for being connected to a bonding pad 210 of a substrate 200 through a solder material 220 (as shown in FIG. 1B), such that the LED chip 130 is electrically connected to the substrate 200 through the leads 124. At this time, the LED chip 130 is suitable for receiving a current through the leads 124 to emit light.
It should be noted that when the LED chip 130 receives the current to emit light, the temperature of the LED chip 130 rises. In the conventional art, the die pad 122 is connected to one of the leads 124 to prevent the high temperature that influences the lifetime of the LED chip 130. At this time, the heat generated when the LED chip 130 emits the light is conducted out of the encapsulant 110 through the lead 124 connected with the die pad 122, so as to reduce the temperature of the LED chip 130.
However, in the conventional art, the leads 124 are mainly designed to serve as electrodes exposed outside the encapsulant 110 of the LED chip 130 instead of dissipating heat, and the surface area of the leads 124 exposed outside the encapsulant 110 is small. Therefore, the heat dissipation effect of the conventional LED package structure 100 is unsatisfactory, and the lifetime of the LED chip 130 is also influenced as the temperature is too high.